https://github.com/srujayreddy/custom-unix-shell
A custom Unix shell implemented in C, featuring piping, redirection, command history, and process management. Built to explore system-level programming concepts.
https://github.com/srujayreddy/custom-unix-shell
academic-project automation-scripts c-programming concurrent-processing custom-shell piping-redirection process-management systems-programming unix-shell
Last synced: 6 months ago
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A custom Unix shell implemented in C, featuring piping, redirection, command history, and process management. Built to explore system-level programming concepts.
- Host: GitHub
- URL: https://github.com/srujayreddy/custom-unix-shell
- Owner: SrujayReddy
- Created: 2025-01-17T03:47:46.000Z (9 months ago)
- Default Branch: main
- Last Pushed: 2025-01-18T04:23:21.000Z (9 months ago)
- Last Synced: 2025-02-13T01:55:37.564Z (8 months ago)
- Topics: academic-project, automation-scripts, c-programming, concurrent-processing, custom-shell, piping-redirection, process-management, systems-programming, unix-shell
- Language: C
- Homepage:
- Size: 12.7 KB
- Stars: 1
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Custom Unix Shell (`wsh`)
## Overview
`wsh` is a custom Unix shell that replicates and extends the functionality of traditional Unix/Linux shells. It was developed as part of the **CS 537: Introduction to Operating Systems** course at the University of Wisconsin–Madison. This project provides hands-on experience with process management, inter-process communication, and system-level programming.
---
## Key Features
- **Command Execution**: Run standard Unix/Linux commands and scripts seamlessly.
- **Command History**: Store and reuse previously executed commands for enhanced usability.
- **Environment Variables**: Manage local variables with a custom-built hashmap.
- **I/O Redirection**: Support for input/output redirection and piping between processes.
- **Batch Scripting**: Execute `.wsh` script files for task automation.
---
## Purpose
This project was designed to:
- Deepen understanding of operating system concepts through practical implementation.
- Master system calls like `fork()`, `execvp()`, and `pipe()`.
- Improve resource utilization techniques and process management.
- Enhance skills in C programming and Unix/Linux system programming.
---
## Technical Implementation
### Command History
The shell uses a **circular array** to manage command history efficiently, storing a fixed number of commands and discarding the oldest as new commands are added.
### Environment Variables
Environment variables are handled using a **hashmap with chaining** to resolve collisions, enabling quick and efficient storage and retrieval of local variables.
### Piping and I/O Redirection
The `pipe()` system call is used for inter-process communication. More advanced execution scenarios are supported through redirection of standard input (`stdin`) and output (`stdout`) using `dup2()`.
### Process Management
Core system calls like `fork()` and `execvp()` are utilized for process creation and execution, ensuring concurrent process handling and efficient resource usage.
---
## Getting Started
### Prerequisites
- **Operating System**: Unix/Linux
- **Compiler**: GCC or any compatible C compiler
### Installation
1. Clone the repository:
git clone git@github.com:SrujayReddy/Custom-Unix-Shell.git
cd Custom-Unix-Shell
2. Compile the code:
gcc wsh.c -o wsh
3. Run the shell:
./wsh
---
## Usage
### Basic Commands
Run standard Unix/Linux commands:
ls -l
pwd
### Piping
Redirect the output of one command as input to another:
ls | grep ".c"
### Input/Output Redirection
Redirect input and output to/from files:
cat < input.txt > output.txt
### Command History
Access previously executed commands:
history
### Batch Scripting
Write commands in a `.wsh` script file:
echo "Hello, World!"
mkdir new_project
cd new_project
Run the script:
./wsh script.wsh
---
## Challenges & Learning
This project helped me:
- Master **system-level programming** concepts like process creation, signals, and inter-process communication.
- Implement complex functionalities such as **piping** and **I/O redirection** efficiently.
- Debug and optimize **resource management** and edge-case handling in a concurrent environment.
---
## Future Enhancements
- Add support for job control features (`fg`, `bg`, `jobs`).
- Enhance scripting with loops and conditionals.
- Introduce customizable shell prompts and aliasing.
---
## License
This project was developed as part of the **CS 537: Introduction to Operating Systems** course at the University of Wisconsin–Madison. It is shared strictly for educational and learning purposes only.
**Important Notes:**
- Redistribution or reuse of this code for academic submissions is prohibited and may violate academic integrity policies.
- The project is licensed under the [MIT License](https://opensource.org/licenses/MIT). Any usage outside academic purposes must include proper attribution.